<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8" />
		<title>求1 + 3 + 5 + ...99</title>2500
	</head>
	<body>
		<script>
			var i;
			var a = 0;
			for(i = 1; i <= 100; i++ ){
				if (i % 2 != 0) {
					a += i;
				}
			}
			console.log(a);
		</script>
	</body>
</html>